In food and drink packaging, there is frequently a demand for a high level of barrier with respect to gases, water vapor and flavors. Use is therefore usually made of polypropylene films which have been metalized or have been coated with polyvinylidene chloride (PVDC). Metalized polypropylene films, without special pretreatment, have a modest oxygen barrier, and they have poor adhesion between the metal layer and the polypropylene layer. The metal layer can therefore easily be damaged (scratched) with loss of barrier. Metalized polyester films generally have a significantly better barrier with respect to, for example, oxygen, and also somewhat better metal adhesion than untreated polypropylene films, but the danger of damage to the metal layer is also present with metalized polyester film. A PVDC layer also provides a barrier, but layers of this type have to be applied from a solution in a second operation, and this considerably increases the cost of the packaging. Ethylene-vinyl alcohol copolymers (EVOH) likewise exhibit a high barrier. However, films modified with EVOH have particularly severe moisture sensitivity, and this limits their scope of application. Due to their poor mechanical properties, they are also relatively thick or have to be laminated with other materials at high cost. They are, furthermore, difficult to dispose of after use. In addition to this, some raw materials are not approved by the authorities or are unsuitable for producing food and drink packaging.
It is therefore an object of the present invention to provide a biaxially oriented polyester film which is simple and cost-effective to produce, has the good physical properties of the known films, has good adhesion to a layer applied by metalizing, and does not give rise to disposal problems.